This is the 1626th most frequent Japanese word.
楽しかっ
The word "楽しかっ" is the stem of "楽しかった," meaning "was fun" or "was enjoyable" (past tense).
Here, '楽しかった' (tanoshikatta) is used to describe a past tense positive and pleasant experience, emphasizing enjoyment.
昨日のパーティーは本当に楽しかったです。
Yesterday's party was really enjoyable.
In this sentence, '楽しかった' is used in a hypothetical or rhetorical question format, implying enjoyment of the experience being referred to.
新しい映画を見るのは楽しかったでしょう？
Watching the new movie must have been fun, right?
Here, '楽しい' (tanoshii) is used to express a general state of enjoyment in the present tense and habitual sense.